In conventional manner, the "integrated optical" technique can be used to make waveguides in a dielectric substrate, generally made of glass, by locally increasing the refractive index of the glass. This can be done by means of an ion diffusion method or by a method of depositing appropriate layers on the substrate.
Such integrated optical components are being used more and more in the fields of transmission using optical fibers. One of the problems encountered in industrial production of such optical integrated components, in particular components such as couplers, bears on the way optical fibers must be aligned with very great accuracy relative to the waveguides created in the substrate. The accuracy of this alignment is of the order of a micron, and is sometimes even less. It is difficult to achieve because of the poor mechanical strength of optical fibers.
To solve this problem, document FR-A-2 612 301 (equivalent to EP 0 283 203) describes an integrated optical component in which the glass substrate comprises a central portion in which the waveguides are formed together with two end portions at opposite ends of the central portion, which end portions include fiber-positioning grooves and grooves for leaving clearance for the fibers. The substrate is precision molded together with its fiber-positioning grooves. The waveguides are made in the central portion of the substrate with the ends of the waveguides being aligned with the fiber-positioning grooves that already exist on the substrate. The fiber-clearance grooves are disposed transversely to the positining grooves and to the waveguides, and preferably after the waveguides have been formed, by mechanical machining. They are at opposite ends of the central portion and they are adjacent to the ends of the waveguides in order to define an interface shoulder on either side of the central portion for the purpose of coupling the fibers to the waveguides.
The positioning grooves enable the stripped fibers that they receive individually to be brought approximately into alignment with the ends of the waveguides and they enable the ends of the fibers to be put substantially into contact against the corresponding interface shoulder. With the fibers positioned in this way, they are held in their positioning grooves, and they are bonded to the substrate by means of adhesive while their ends in the clearance grooves remain free.
The clearance grooves then make it possible to obtain final accurate alignment between the fibers and the waveguides prior to bonding the ends of the fibers against the corresponding interface shoulders. This final accurate alignment is achieved by means of a micro-manipulator whose grasping component is capable of grasping the free ends of the fibers in the gap provided by each clearance groove. This final adjustment serves to compensate for the lack of sufficient precision in alignment (which is difficult to obtain) between the waveguides and the positioning grooves that are molded in the substrate.
In that integrated optical component, the clearance grooves provided to leave the ends of the fibers free for the purpose of final adjustment by micro-manipulation, suffer from weakening the fibers mechanically once alignment has been obtained and their ends have been finally bonded in position. This final bonding becomes fragile: it makes it difficult to withdraw the micro-manipulator engaged on the ends of the fibers and it is highly sensitive to environmental conditions, particularly when the final adjustment performed by the micro-manipulator is relatively large.
An object of the present invention is to avoid these drawbacks.